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# Sound Waves

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### Sound Waves

1. 2. <ul><li>How would you draw something you cannot see? </li></ul>Try drawing a sound wave.
2. 4. Sound is a wave with recognizable characteristics. Sound waves can pass through solids, liquids, and gases.
3. 5. <ul><li>Sound waves are a type of mechanical wave – </li></ul>Sound is a longitudinal wave Rarefactions are regions in which the medium particles expand farther apart. In between the compressions and the rarefactions, You can think of the compressions like crests, Sound waves are a type of mechanical wave – a longitudinal wave. In between the compressions and the rarefactions, the medium exists in its normal (at rest) state. You can think of the compressions like crests, and the rarefactions like troughs. These waves consist of a series of compressions and rarefactions. Compressions are regions in which the medium particles are pushed together.
4. 6. <ul><li>Sound, as a mechanical wave, must have a medium through which to propagate. </li></ul>Not only does the medium enable the propagation of the wave, The energy that produces the force to set the medium in motion can vibrate massive particles much less than it can vibrate particles with smaller masses. Not only does the medium enable the propagation of the wave, it also affects the characteristics of the wave. Take different gas molecules for example.
5. 7. The medium affects sound waves Since materials consist of particles, the type of connections between the medium’s particles can also affect how sound waves propagate. Since materials consist of particles, You may remember that longitudinal waves can pass through solids, You may remember that longitudinal waves can pass through solids, liquids, You may remember that longitudinal waves can pass through solids, liquids, gases, You may remember that longitudinal waves can pass through solids, liquids, gases, and even plasma. The closer or the more stiffly connected the particles of the medium, It is for this reason that sound travels faster through water (L) than air (G), and even faster through ice (S) than water. The closer or the more stiffly connected the particles of the medium, the faster the sound wave propagates through it. If the sound travels at different speeds, The same sound will seem different to creatures listening through the ground, the water, and the air. If the sound travels at different speeds, the pitch must change with the medium. Not only would it sound different, each type of creature has its own way of picking up those waves. It is for this reason that sound travels faster through water (L) than air (G), ice water air
6. 8. During class, you place your head down on the desk with your ear against the surface. Would you expect the sounds of your teacher reprimanding you to sound higher pitched or lower pitched?
7. 9. <ul><li>Reading: </li></ul><ul><li>Activity: </li></ul><ul><ul><li>Name that Tune </li></ul></ul><ul><ul><li>Sound Off </li></ul></ul>
8. 10. Stretching to the Limit @ Home Animals from elephants to insects are known to use infrasound (below human hearing) for communication, and seismic waves for early warning of earthquakes. Do you think it possible for people to learn to be forewarned of earthquakes by cues from these animals?
9. 11. <ul><li>Sound wave compressions are like , while rarefactors are like . </li></ul><ul><li>2. Name two animals with weird ears. </li></ul>
10. 12. Review for investigating on the Internet. web links
11. 13. State Objectives Student Workbook Student Workbook Key Notes / Lesson Overview
12. 14. 1. Sound wave compressions are like crests , while rarefactions are like troughs .
13. 15. <ul><li>2. There are lots of animals with weird ears. Crickets have ear drums on the surface of their legs. Moths have eardrums on their wings. Frogs have ear drums located behind each eye. </li></ul>